This is the second part of my account of the emergence of today's modular electric locomotives.

Their job is... BLS class Re 485 008 and a sister (Bombardier TRAXX 1 family, type TRAXX F140 AC1) with a freight train in north–south transit across Switzerland, reached Lalden on their descent of the south ramp of the old Lötschberg route, 25 May 2007. Photo by user Titane8226 from Wikipedia

This is a journey into industrial history – with sub-plots about technological advances, merger mania and neoliberal excesses, political and intra-company intrigues, and European unification.

The first part traced the origins in a wholly different project: the universal locomotive, which can pull any kind of train, a cost-benefit win for integrated national railways. The innovations enabling such a loco were named: asynchronous AC motors and high-power semiconductors. On the example of running gear, I gave a first indication of what led to modular: the possibility of "dumbing down" the universal.

In this diary, I will trace the rest of the – still far from straightforward – development for each of the three main makers separately.

Siemens: Eurosprinter

For long, West German electric loco makers produced almost only for the domestic market. That changed with the DB class 120 technology (shared among West German makers). From 1991, Siemens got to deliver 75 locos to Spain (RENFE class 252; see also this diary).

The locos were for two voltage systems different from the one in Germany (3 kV DC on old lines, 25 kV, 50 Hz AC on high-speed lines). But, with the new power electronics, it proved rather simple to build supply units for the same on-board DC main circuit. So, the idea arises: with relatively minor modifications, aint' the universal loco suited for export into any country? Indeed, after the first batch for Spain, Siemens built an up-powered (from 5.6 to 6.4 MW) prototype for themselves, and christened it EuroSprinter.

The wide nose of the EuroSprinter demonstrator can't deny its Iberian broad-gauge origins.127 001 descends the Geislinger Steige (one of the very first railway mountain crossings) with an InterRegio on 5 March 1994. Photo by Werner Brutzer from Bahnbilder.de

Exports to Portugal (CP series 5600), Greece (OSE class 120), Denmark (DSB class EG = series 3100), even South Korea (Korail class 8200) proved Siemens right. However, the EuroSprinter platform wasn't yet too stable and flexible: each major order from the two home markets resulted in significant redesigns. Two of these pointed the way into the future.

One was a freight loco to realise another kind of universality: running under all four main voltage systems in Europe. Developed for DB (class 189), it got the company type name ES64F4. It was sold to DB, SBB, and several private operators and leasing companies.

The ES64F4 (for EuroSprinter 6.4 MW/freight service/4 voltage systems) has the narrower cross-section suited for, for example, France. Horizontal stiffeners on the sidewalls enabled weight savings elsewhere.189 700, made for Romanian private freight operator CTV, was fresh out of the factory when caught in Treuchtlingen on 6 April 2009. Photo by Albert Hitfield from railcolor.net

The other is the "Taurus" family for Austria's ÖBB (already introduced in Railjetting into Red Bull Country). It spawned several orders from other operators, and got the Siemens designations ES64U1 and ES64U2 (for 6.4 MW/universal service/1 resp. 2 voltage systems).

Then, ÖBB revised its order, wanting 3-voltage-system locos. This led Siemens to properly merge the Taurus and multi-system platforms: basically, an ES64F4 interior inside a reduced-cross-section Taurus exterior was put on Taurus running gear; and, in 2005, the ES64U4 was born. The power electronics was also updated (using IGBT in place of GTO – which also means that they no longer sing the octave when starting).

To save weight for the extra equipment for the third voltage (DC), the Taurus 3 got a smaller transformer, reducing max power (to 6 MW). So the consistent Siemens designation would have been ES60U3 – ah well...Austria is a special case in the bright new open-access world: not only was it reluctant to divide ÖBB's locos between its operating branches, but it hindered the entry of foreign locos with "track-tearing" running gear on its rails. Thus most freight operators use Tauri.Northbound 1216 910 of Slovenian-Austrian company Adria Transport at Werfen, south of Salzburg, on 4 December 2008. Photo by Manfred Wolf from Bahnbilder.de

Now Siemens had its modular platform to produce electric locomotives for any need: DC, AC, both; universal, or cost-effective freight. Yet, it took only two years until the next redesign: the EU introduced new standards for cabs. Siemens took this as occasion to also merge the electric EuroSprinter with the diesel-electric EuroRunner platform (without re-designating them).

The new Portuguese Railways CP series 4700, Siemens type ES64B1, is a light freight-and-passenger version, with a broken nose borrowed from the EuroRunner diesel sisters.CP 4713 between Vale do Guizo and Somincor (south of Lisbon, Portugal) on 1 April 2009. Photo by user nmorao from Flickr

Once upon a time, there was a Swedish electronics giant named ASEA, and a Swiss one named Brown, Boveri & Cie. (BBC); both with a proud history of producing locomotive electrical parts. BBC in particular was already a small empire, present in Italy and Germany. In 1988, the two merged into ABB.

ABB continued to expand. In 1990, it acquired one of the main makers of locomotive main parts in Germany, Henschel – so now it could make locos entirely in-house. Meanwhile, a rival electronics giant, AEG (itself owned by Daimler-Benz, the maker of Mercedes cars), "got back" the big East German locomotive maker, LEW (see end of first part), on account of LEW having started out as a nationalised AEG factory.

The empire was truly born in 1996: when ABB and Daimler-Benz merged their railway business in a joint venture, ADtranz (this horrible letter soup was an acronym for ABB Daimler Benz tranzportation, with a spelling error meant to imply a complete product palette – "from A to z" –; something only managers can find inspiring).

ADtranz was a product of the times: the opposed trends of merger mania and shedding non-core business. Though ADtranz had trouble merging its many parallel product platforms, it continued to expand voraciously, in particular in the then EU accession countries: in the end, it was a monster with factories and subsidiaries from England to Bulgaria.

While ADtranz's expansion developed into a case of imperial overstretch, its owners wanted out. First ABB left in 1999 (when the company was re-named "DaimlerChrysler Rail Systems" on paper). Then DaimlerChrysler had enough (having got enough problems of its own), and sold most of the ruins to Bombardier in 2001.

Bombardier was a Canadian company that originally had nothing to do with railways: it started with snowmobiles, later got into airplanes. However, after some twists and turns, it became the main maker of passenger coaches (in particular bi-level) in Canada and then North America. It then went on to acquire troubled companies in Europe: BN (the main maker of Belgian locos and EMUs, 1988), ANF-Industries (big French EMU maker, 1989), Talbot (West German EMU and coach maker, 1995), DWA (big East German coach maker, world's biggest double-deck maker, 1997).

So, with ADtranz eaten, the end result was an even bigger empire – though Bombardier managed it more wisely.

ABB/ADtranz/Bombardier: Lok 2000/Eco2000

Now, back in the nineties, in ADtranz, the dominant ABB part wanted its technology to supersede all else. And indeed they looked predestined for that:

then ABB could develop and build a Swiss lineage, peaking in the "Lok 2000" (in service as the freight-and-express Re 460 for SBB and Re 465 for BLS; and as exports to Norway: NSB class El18, and Finland: VR class Sr2);

then used its expertise to develop its own concept of a universal loco with modularity, the "Eco2000", with which it won the order for DB's new express locomotive (class 101).

Very characteristic of the Lok 2000 family was the high roof shrouding. The large plow is part of the arctic modifications. NSB [El] 18 2250 waits in Oslo C on 14 February 2006. Photo by Dag Eidet from RailPictures.Net

However, the Swiss-German ABB lineage proved a dead end. On one hand, all of the above types were suffering from various persistent teething problems. On the other hand, they weren't cheap. And, for once, the better technology (even if dumbed-down) won against all obstacles erected by company politics.

Bombardier: TRAXX

Back when Siemens presented the EuroSprinter, AEG responded by building its own prototype of a universal locomotive for all customers: the 12X.

Two visible innovations of the 12X remained oddities not used in later locos: a short wheel distance in the bogies; and the "blades" formed by the (white) sidewalls protruding beyond the (red) cab front, meant to give stability against wind.The 12X, as it appears now with the logo of its latest owner, with a test train in Sion (Switzerland) on 19 July 2005. Photo from Voielibre

However, when DB's big order came – not for a universal loco but separate locos for its operating branches –, AEG came short: while Siemens and ABB got the big orders for high-power locos in the hundreds, AEG was only tasked with 80 locos for medium-heavy freight (class 145) – a severely dumbed-down 12X. As implied in the first part, these locos got a cheaper but cruder running gear on account of their low top speed.

AEG went under in ADtranz before the first was built (in 1997), so some of the electronics was ABB. But only part, and none of the running gear – which proved a relatively good construction (less rail-tearing than the Siemens rivals). What's more, the class 145 went into service without a hitch, while the Siemens and ex-ABB big sisters suffered teething problems.

The front-edge 'blades' are gone; however, DB made the continuation of the sloped roof edge down the front a styling requirement for all its new purchases. (Possibly not unrelated: the then DB boss was a former AEG CEO.) Rail4Chem, a merger of chemical industry railways, was one of the first open-access private freight operators in Germany – and also among the first private buyers of the 145 family. 145-CL 005 (and an EMD-made "class 66" diesel) with a chemical transport near Halle-Zscherben on 16 March 2005. Photo by Michael Mösken from Bahnbilder.de

From there on, the success of the family originally named "145" (borrowing its first customers' designation) came in small steps:

DB's sudden need for some extra locos to pull double-deck coaches could be solved on short order with modified 145, then a version with proper hollow shaft drives (146.0, 2000);

also as stopgap measure, DB wanted a two-voltage-system version for new cross-border traffic – this grew into a giant order for 400 locos (class 185, 2000);

a heavy-haul twin version for the Luleå–Narvik iron ore railway in the far north of Sweden and Norway, though ordered back in the AEG years, got much publicity (MTAB class IORE, 2000/1);

an order from SBB resulted in an up-rating (from 4.2 to 5.6 MW: class Re 482, 2002)

using its expertise from Italy (more on that in a moment) to cut development time to a minimum, Bombardier offered and delivered a 4-voltage-system version to SBB (class Re 484, 2004).

With several orders trickling in from the emerging private freight rail operators in the meantime, it was unsurprising that Bombardier chose this family as their modular platform. In 2003, it finally got a company product name, TRAXX (again, how could someone get paid for inventing such bland names?...).

In 2005, under the name "TRAXX 2", the design was updated: chiefly power electronics (GTO to IGBT change) and cab (due to new EU regulations, just like Siemens).

The elegant contours of the lower front are gone, but there is improved crash resistance. Spanish state railways RENFE class 253 (most of which will be built in Poland [frame] and Italy [electronics]) is a TRAXX F140 DC, the DC-only freight version that's new in the 2E family (see below).RENFE 253 002 in Pola de Lena on 16 May 2008. Photo by Edgar Fernandez Canteli from railcolor.net

Bombardier was also first (a year ahead of Siemens) to extend its platform to diesel-electrics, with the result called TRAXX 2E.

The TRAXX P160 DE: 160 km/h diesel-electric passenger version of the TRAXX 2E.246 005 (owned by a public company created by three north German states and operated by private company Metronom) leaves Cuxhaven for Hamburg with a double-deck train on 18 February 2008. Photo by Malte Werning from railcolor.net

TRAXX 2E also absorbed ADtranz/Bombardier's third in-house electric loco lineage, which I didn't mention so far: locos running (primarily) under DC overhead lines made in Italy. This lineage started with own shell and mechanics and ABB electronics, then some parts of the "145" were incorporated, justifying the nominal "TRAXX" designation when the brand name was introduced.

The FS class E464 is a one-ended locomotive for push-pull trains built since 1999, which became "TRAXX P160 DCP" in the TRAXX 1 family. It survived newer sisters, and is to remain in production alongside the TRAXX 2E until 2010: no less than 538(!) will run across Italy.E464-008 with a passenger train in Riomaggiore on 23 July 2007. Photo by W. Kolins from RailFanEurope.net

Alstom: Prima

Back in the era when the universal locomotive was all the rage, French state railways SNCF and its biggest supplier, then called GEC-Alsthom, bet on the wrong technology.

On one hand, they still believed that one motor per bogie (i.e. two wheelsets) is more economic (less maintenance). On the other hand, they went for the synchronous AC motor. That was good enough for second-generation TGVs, but, while the power of the DB class 120 could be matched at the time, asynchronous AC motors had a higher potential. Thus the locos delivered to SNCF (series 26000, 1989) remained the sole representatives of the project/product name "SYBIC".

Edges all around: SNCF 26148 with a night train from Strasbourg nears Nice along the Riviera, at Anthéor on 2 August 2007. Photo by Ian Leech from RailPctures.Net

GEC-Alsthom corrected the mistake when SNCF converted the last batch of its order into one for triple-voltage-system locos for cross-border traffic (SNCF series 36000, 1997), creating the "ASTRIDE" asynchronous AC locomotive platform. GEC-Alsthom could now sell a universal (well, express/freight) version on its traditional BeNeLux export market (Belgium: SNCB class 13, Luxembourg: CFL series 3000). However, that was it.

The ASTRIDE locos were stylish, but they still have traditional sidewall cooler fans.CFL No. 3014 with an IR to Luxembourg emerges from the mist at Poulseur on 2 March 2009. Photo by Eddy Konijnendijk from RailFanEurope.net

So, using the next SNCF order as occasion, the company set out to create a leaner-meaner modular design of its own: the PRIMA platform (for SNCF, series 27000, 27300 and 37000). A diesel-electric version was created in cooperation with Siemens (series 75000).

With the PRIMA I, Alstom finally put the air intake on the roof. The bulbous nose however hides what was an advantage vs EuroSprinter and TRAXX at the time: good crash-resistance.SNCF [4]37052 (a "PRIMA EL 4200 B 3U15 Fret", for electric/4.2 MW/two wheelsets per bogie/triple-voltage with 1.5 kV DC/freight) near Siebnen in Switzerland on 27 July 2007. Photo by Eddy Konijnendijk from RailFanEurope.net

That's less surprising considering that the PRIMA family wasn't yet complete, it was where TRAXX was years earlier: what existed already was a comparatively weak loco with a few variants and long delivery times. Alstom conducted long tests with an up-rated (from 4.2 to 6 MW), 4-voltage-system test unit, the PRIMA 6000. At the end of it, there was a complete overhaul - also of production methods.

The full-power four-voltage-system PRIMA 2 prototype was rolled out this month, on 3 June, but approval for regular service across Europe is expected only for 2011, after extensive tests. However, launch customer is Morocco's ONCF: 20 locos in a simpler version are to be delivered from this summer.

Beyond the three giants, what else remained on the electric locomotive market? Really, not much.

The one I take most seriously is koda Transportation/Czech Republic. Alone in the new EU members, it could survive as an independent maker. At last last year, it presented its 109E (ČD class 380; left on photo below), a maximum version (6.4 MW, 3-voltage-system, 200 km/h). It will sustain their domestic near-monopoly (see Trains in Moravia). As for exports: depends on eventual teething problems & production quality.

Talgo/Spainmade the prototype of a high-speed loco (right on photo above). But as it is weak (3.2 MW), and as RENFE ordered TRAXX; it should be more seen in the light of Talgo's ambition to produce power units for its high-speed trains in-house.

AnsaldoBreda/Italy is the second main supplier of FS. However, its current loco product (FS class E403) failed to achieve service-readiness for years now (the likely reason it is delayed with its Danish and BeNeLux exports, too) -- the future is dark for this company.

The dark horse competitor is ZNLE/Poland. The maintenance shop turned manufacturer builds the prototype of E6ACT, a six-axle freight loco.

Russia and Ukraine are special cases. There is significant domestic locomotive production, protected by a reluctance to import complete foreign designs. Indeed Transmashholding/Russia is alone keeping producing new locos with wound-field motors. However, makers of both countries made modern asynchronous AC locos by teaming up with the three Western European giants for components.

Its GTO-VVVF propulsion system was supplied by Siemens. The ability to produce a "fa-so-la-ti-do-re-mi-fa-so" scale when the propulsion starts up quickly became a signature to the 2100 series when it was introduced, earning the nickname as the "singing train" (歌う電車). Subsequently, similar propulsion was also installed on 56 cars of the N1000 series. The uniqueness of the propulsion system made its way into various music and popular culture, such as Super Bell"Z. However, it was reportedly expected that this feature may soon disappear, as substitute parts are no longer available when the propulsion system is due for replacement in a decade or earlier.

EMD and GE make diesel-electrics, not electrics. (Their European exports will feature in a future diary on modern diesel heavy-haul in Europe.)

Apart from four failed prototypes (AC4000, DJ - this one with ADtranz motors and locally-made inverters -, DJ2, Tiansuo), the Chinese makers' modern locos were all technology transfers, from all three of the big European makers plus one from Japan.

A picture of the newest of the Chinese technology import locos, the HXD3B (which is the world's most powerful non-multiple loco with a continuous power rating of 9.6MW), with a picture of the origin of its exterior, the IORE double locomotive:

A picture of what was the pinnacle of domestic development, the SS9[G]; which has wound-field motors (and a continuous power rating of only 4.8MW on six axles), which got an external styling retro-engineered from the ABB Lok 2000 exported to Hong Kong:

Back in the era when the universal locomotive was all the rage, French state railways SNCF and its biggest supplier, then called GEC-Alsthom, bet on the wrong technology.

On one hand, they still believed that one motor per bogie (i.e. two wheelsets) is more economic (less maintenance). On the other hand, they went for the synchronous AC motor. That was good enough for second-generation TGVs, but, while the power of the DB class 120 could be matched at the time, asynchronous AC motors had a higher potential.

To which I should add: a variation on the synchronous AC motor (in which the magnetic fields and the rotor rotate at the same speed, i.e. synchronously), the so-called "permanent magned synchronous motor", is actually the Next Big Thing. And just Alstom is the leading developer.

The permanent magnet motors are even more efficient, and that on a much wider rotational speed range. While the practical difference in efficiency is miniscule (say 95% vs 98%...), the permanent magnet motor can do without gears: meaning, it can be built around the wheelset axle (resp. hollow shaft), a direct drive. (Again the parallels with wind power technology...) Sparing the gears also means further weight reduction.

Here is an illustration íi found for a Siemens application, with the traditional motor-gears-wheel on the left and a new direct drive on the right:

As yet, the permanent magnet motor is only used in lighter trains (the top use being in Alstom's AGV high-speed train). For scale: the AGV's motors are rated at 760 kW, while state-of-the-art asynchronous AC locomotive motors are rated at 1600 kW. But, I'd expect permanent magnet motors in a heavy-duty locomotive to come in the next decade.

Of course the wild card for freight use is, what will a permag-motored freight locomotive cost? This is one of the biggest reasons for Bombardier dominance. The Siemens locomotive was sized a little too powerful, for most freight use. The greater power came with a higher-price tag. I suspect that Siemens would have had even fewer orders, if Bombardier wasn't producing at capacity. The TRAXX 2E variants come from the bodyshell being designed to accomodate the diesel engine variant, mainly the radiator openings. Otherwise there is no significant difference from the TRAXX 2 model. All the F140AC2 (DB Class 185, SBB Re482, etc.) variants still use the TRAXX 2 bodyshell, as DB and Bombardier are unwilling to risk potential homologation problems, from a change in the bodyshell. All Siemens ES64F4 locomotives use IGBTs in their power conversion equipment as do all the ES64U series locomotives (Taurus). Siemens first IGBT locomotive was DB Cargo's 152190 (This locomotive was intended to be 152032). The 152 (and the Alstom Prima I) suffer from poor tracking at speed, resulting in excessive track forces, which is why they never received authorization in Austria, and why the Prima I only has limited approval in Germany and Switzerland. The ES64F4 solved this problem by using an active yaw-damper on the trucks.

Of course the wild card for freight use is, what will a permag-motored freight locomotive cost?

Indeed that's a question -- but, given how asynchronous AC pushed out wound-field DC, I don't think it's impossible if the technology becomes mainstream in more high-quality passenger vehicles.

I suspect that Siemens would have had even fewer orders, if Bombardier wasn't producing at capacity.

...and if

The 152 (and the Alstom Prima I) suffer from poor tracking at speed, resulting in excessive track forces, which is why they never received authorization in Austria, and why the Prima I only has limited approval in Germany and Switzerland.

The ALP-46 locomotives supplied to the US are like the German Br 101 locomotives, in that they use one Traction Converter per axle, while all European TRAXX locomotives use one Traction Converter per bogie.

One final comment for tonight the change in rating for Bombardier TRAXX locomotives from 4200kW to 5600kW was a software change only, the change allows the higher output for One-Hour, while 4200kW remains the Continuous rating for the locomotive. The German Br 145 locomotives can receive this change if their owners so choose.

Hm. If that's your source, I think Wikipedia errs in that. AFAIK 5.6MW is the new continuous rating, for which, as you say, a software change was enough, given that everything else came from a loco scaled for 6.4MW. I couldn't find a definite source (Bombardier saysDauerleistung = continuous power, but that may be a marketing 'mistake'), but in a forum where locomotive drivers debating just this subject, one posted this photo he made in a TRAXX 2 that ran in double, showing a higher temporary rating on a mountain climb ("Primärleistung" field):

Very interesting photograph, one tidbit of information not shown, would be of great interest to me, that is the Tractive Effort in kN. Power Consists (sets of locomotives coupled together) are limited on the Gotthard to a maximum of 600 kN, by the strength of the Drawgear. Anymore and you get into the safety margin, and might pull the train apart by breaking a coupling. I had been lead to believe that at above 5.6 MW the locomotive would produce more than 300 kN if the grade was steep enough to prevent the train from accelerating.

From what I know, maximum tractive effort is a pretty strict limit software-side on the modern electrics, so it shouldn't go above.

Power is speed times force, so I'd think that doesn't tell much about grade climbing. Extra tractive effort on a slope is train mass x g x grade. So, ignoring force needed for acceleration and train resistance at standstill, for the Lötschberg mountain line maximum grade of 2.7%, 300kN would in theory be enough for 1130 tons (while 2x300kN would do it for 2260 tons). The locos are rated for 650 tons at that grade.

(Back to power, 5.6MW is enough to maintain 300kN up to a speed of 67.2 km/h.)

Perhaps the two diagrams below will tell more about TE as function of speed than the above words.

The first is for the Vossloh Euro 4000 diesel -- as typical for six-axle heavy diesels, it shows a monotonous decline with speed, and the maximum power hyperbole (where TE ~= max power/speed) is reached very quickly:

Now here is the graph for the BLS Re 465, a four-axle high-power electric, under ideal conditions; with dashed curve for when the loco utilises only maximum continuous power, and the parallel solid curve for when it uses maximum one-hour power:

Under ideal weather conditions, before reaching the maximum power hyperbole, traction control limits TE to the rated maximum very strictly. (From actual measurements done on one new high-power loco by colleagues, I'd say precise to the kN.)

Well for me the epiphany happened, the photograph shows a figure of 6245kW for Primärleistung whereas the commonly quoted figure for TRAXX locomotives is 5600kW. The key to the difference is in the measurement location
Primärleistung is the input to the Primary Windings of the main transformer, while the 5600kW figure is "Leistung am Rad" at the Wheel, the difference is the losses due to heat and gearing. The difference is roughly 10% which is a commonly accepted figure.

By jove, you're right! Though, methinks part of the 10% for asynchronous AC electrics are auxiliary units.

Later in the same thread, I find this photo, too:

In the first line left is speed, right is target TE; the second line shows the target TE per bogie, the third line shows actual TE (from which power is just under 5.6MW); the next lines show target power in and out, then the actual metered electric powers, then the electric loss.

Unfortunately, the photographer doesn't say anything on continuous/one-hour, he just says the software menu of his locomotive [one of the first class 185 which was up-rated from 4.2 MW with the software change] said "5.6 MW". However, just found another locomotive driver in the thread claiming:

Could very well be that the hourly and continuous ratings aren't meaningful anymore. I was told by an knowledgeable source that beginning with 185_051 for DB and 185_510 for the private operators all were built rated at 5.6 MW. This of course includes all Swiss owned locomotives. It was planned to upgrade the earlier DB locomotives, but perhaps this was never done. None of the earlier DB locomotives is homologated for Switzerland, but 30 are homologated for Austria.

Could very well be that the hourly and continuous ratings aren't meaningful anymore.

Having thought about it - I think lack of distinction should mean that maximum power is limited by temperature control only. That may or may not be fair to customers, depending on the level of heating: if full power is available in winter, but not in the summer, then the same trains can only be run slower in the summer -- and the differene is not guaranteed by the maker. This should not be an issue for the BLS and SBB locos, which utilise de-facto one-hour maximum power on climbs, but it may be an issue elsewhere.

It was planned to upgrade the earlier DB locomotives

See half-sentence in brackets in my previous comment: the earlier class 185 were upgraded, the photo shows one of them (but the class 145 wasn't AFAIK).

Yep, no TRAXX with single axle control yet -- nor with 6.4MW and 200 km/h. It is interesting to note that in the lineage leading to the Baureihe 101, the switch from single bogie control to single axle control was between the SBB Re460 and the BLS Re465.

I don't have the weight for a Re465, but if it weighs 85 tonnes, then your wheelslip system needs to achieve a factor of adhesion of 38% to produce 320kN of pull, or 36% to produce 300kN. The later figure is reasonable, while the former is possible but has significantly larger risks, especially where delays caused by a stalled train cause cumulative delays to the whole system.

A drop from 38% to 20% solely due to rain is a terrible performance, and not indicative of a very sophisticated adhesion management system. Both EMD and GE for their modern diesels use a "Creep Control" system to achieve maximum adhesion whereby at speeds above 7 mph. wheel rotation is 7% faster than needed for the current ground speed, also the control computer will reduce power slightly to the leading axle to allow it to "Dress" the contact surface of the rail and eliminate material such as oil or squashed insects (caterpillars and locust are the worst) before the other axles pass. The much greater weight of North American diesels probably is high enough to break the surface tension of most materials likely to be found coating the rails which would help also.

"Dress" = cleaning creep (that's how I translate German Putzschlupf; I don't know if there is a British -> UIC English term) is a real benefit of single axle control - and an advantage of the 'rail-tearing' axle-hung motor Siemens EuroSprinters over the present Bombardier TRAXX locos. (There have been two major comparison tests I read of, one on the steep line to Blankenburg/Harz in Germany with its isolated 25kV/50Hz electrification, another on the Brenner route, with a DB 189 = ES64F4 coming out on top in both cases.) However, on four rather than six axles, that's still a 25% drop in adhesion. (Note that on the aforementioned Blankenburg line, the isolated electrification was dismantled in the end, and six-axle diesels took over.) Then there is sanding (and with that increased sand use and track/wheeltread wear), but that is not always stable, in particular for all four axles. There is also the cleaning brake block - which is not widespread enough across Europe for reasons that appear bureaucratic to me. And, as you say, axle weight is a third of the US, so it's all less stable. (Though still less bad for locos than for even lighter EMUs and DMUs.)

Wheel slip is just a notorious problem even with cleaning creep, sanding and cleaning brake blocks -- softwares are updated repeatedly, and they get national versions.

Siemens is now producing a variant of the ES64F4 for MRCE Dispolok in Italy that lacks the ability to operate under AC power supply. These are numbered E189.4xx by the Italian Authorities. The first 10 were snapped up by Veolia Cargo, SBB Cargo, and NordCargo.